The long-term anal of this research is to understand the pathogenesis of Ebola virus infection at the molecular level. Ebola virus continues to cause outbreaks of severe hemorrhagic fever in humans and other primates. This filamentous, enveloped, non segmented negative-strand RNA virus contains a single transmembrane glycoprotein (GP) that forms spikes on the virion surface and is likely responsible for binding to cell surface receptors and membrane fusion. Little is known about the biological functions of Ebola viral proteins, including the GP. This lack of progress can be traced to the lethality of Ebola virus and the requirement for biosafety level 4 containment imposed by its study. Hence, the proposed research seeks to promote an understanding of the Ebola virus GP through use of an experimental system [based on a recombinant vesicular stomatitis virus (VSV)] that will circumvent stringent biohazard restrictions. The first specific aim is to map the functional domains of the Ebola virus glycoprotein. Regions of the GP responsible for receptor binding and fusion will be determined by mutagenesis of the molecule using the VSV system. Key structural features - including protein acylation, amino acid sequence homologous to the immunosuppressive region in retroviral envelope proteins, and the amphipathic and charged helices in the transmembrane proximal region - will also be examined for functional importance. Aim 2 seeks to characterize cellular receptors for Ebola virus. Preliminary data from the applicant s laboratory suggest that integrin is involved in Ebola virus infection, perhaps serving as its receptor. Hence, the first phase of research will be to test this hypothesis by exposing different integrin subunits. Should integrin not serve as a receptor, an established method will be employed to identify a bona fide receptor. The information generated by this project will greatly expand understanding of the early steps of Ebola virus infection, thus helping to clarify the molecular basis for the unprecedented virulence of this virus. Ultimately, the proposed studies should identify targets for the development of effective antiviral compounds. The VSV system to be exploited will not only abrogate rigid biosafety restrictions in the study of Ebola virus, but will likely serve as a model for research on other hazardous viruses or those not amenable to in vitro culture.